/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.api.common.operators.util;

import org.apache.flink.annotation.Internal;

import java.io.Serializable;
import java.lang.annotation.Annotation;

/**
 * UDf operators can have either a class or an object containing the user
 * code, this is the common interface to access them.
 */
@Internal
public interface UserCodeWrapper<T> extends Serializable {
	
	/**
	 * Gets the user code object, which may be either a function or an input or output format.
	 * The subclass is supposed to just return the user code object or instantiate the class.
	 * 
	 * @return The class with the user code.
	 */
	T getUserCodeObject(Class<? super T> superClass, ClassLoader cl);
	
	/**
	 * Gets the user code object. In the case of a pact, that object will be the stub with the user function,
	 * in the case of an input or output format, it will be the format object.
	 * 
	 * @return The class with the user code.
	 */
	T getUserCodeObject();
	
	/**
	 * Gets an annotation that pertains to the user code class. By default, this method will look for
	 * annotations statically present on the user code class. However, inheritors may override this
	 * behavior to provide annotations dynamically.
	 * 
	 * @param annotationClass
	 *        the Class object corresponding to the annotation type
	 * @return the annotation, or null if no annotation of the requested type was found
	 */
	<A extends Annotation> A getUserCodeAnnotation(Class<A> annotationClass);
	
	/**
	 * Gets the class of the user code. If the user code is provided as a class, this class is just returned.
	 * If the user code is provided as an object, {@link Object#getClass()} is called on the user code object.
	 * 
	 * @return The class of the user code object.
	 */
	Class<? extends T> getUserCodeClass ();
	
	/**
	 * Checks whether the wrapper already has an object, or whether it needs to instantiate it.
	 * 
	 * @return True, if the wrapper has already an object, false if it has only a class.
	 */
	boolean hasObject();
}